The present invention relates to a control mechanism for a pair of jaws for clamping mouldings intended to be stapled together to finally constitute a frame.
A standard stapling machine comprises a work table (see FIG. 1) intended to receive the under surfaces of two mouldings to be stapled, positioned by an operator, and two roughened jaws, with grips, then push the front face of each moulding, i.e. the inside face of the future frame, so as to bring the opposite rear face against one of two respective framing work rest strips forming side stops of the table, mutually perpendicular and delimiting a stapling corner. The two mouldings are thus brought and held according to the desired right-angle orientation, with their ends abutted against each other in this corner. Each jaw thus constitutes a holding jaw by clamping a moulding, cooperating with the associated stop. Thus, the staple will actually penetrate at the desired location in each end section, i.e. will be anchored in the bulk of each moulding.
Once the positioning of the two mouldings has been carried out in this way, a press head, situated above the stapling corner, descends to rest against the front longitudinal edge of the end sections of the two mouldings, in order to act as an upper counter-support to an upturned stapling head situated flush with the surface of the table to insert the staple in the under surface.
Then, the jaws move away from the side stops to release the assembled pair of mouldings, and the operator can then lift them to a level above the jaws to turn the assembly a quarter-turn parallel to the table, in order to place one of the two end sections of this pair which remain free, in position in the stapling corner and staple a third moulding, recommencing these operations once again for a fourth moulding which completes the frame.
Such a machine does indeed allow stapling to be performed correctly, but the manoeuvre that the operator must perform to ensure each time that the previously-assembled mouldings are then presented according to an orientation offset by a quarter-turn, is relatively long and arduous.
In fact, as soon as at least two large-dimension mouldings have been joined, they delimit on the table, with the third, even the fourth moulding, a large obstructive area of the future frame, thus constituting a sort of guardrail which prevents the operator from standing next to the table. The operator is thus working in an awkward position when he lifts the assembled mouldings to disengage them from the jaws, which is not ergonomic.
Another drawback is linked to the fact that the press head overhanging the corner constitutes an obstruction when the operator disengages the stapled mouldings, as this disengagement is carried out by lifting. Therefore at rest, the press head must present a relatively large stand-off distance, but since this stand-off distance is also the distance of travel of the head, the rate of operation is limited accordingly, due to the fact that the speed of travel must remain limited in order to avoid an excessive impact which would risk damaging the mouldings.